1. Field of the Invention
The present invention relates to a printing press including a printing unit and a machining unit which machines a sheet subjected to printing by the printing unit.
2. Description of the Related Art
A container made of a sheet such as paper or the like, for packaging or housing a commodity product or the like therein, is usually manufactured in such a manner that a pattern of the container in a developed state is printed on the sheet by a printing press, a developed portion of the sheet is then punched, and a sheet piece obtained by the punching is assembled. An apparatus has been proposed, in which such processes of printing the pattern on the sheet and punching the developed portion into a predetermined shape (a developed shape of the container) are performed in a series of processes. For example, Japanese Patent Laid-Open Publication No. H1-285338 (published in 1989) discloses a sheet-fed offset/paper container machining apparatus in which a sheet-fed offset press and a puncher are arranged in a series.
Such a printing/machining apparatus (hereinafter, also referred to as a “machining apparatus”) disclosed in Japanese Patent Laid-Open Publication No. H1-285338 also includes a single drive source as in a general printing press. Specifically, the printing press and the puncher are driven by the single drive source. By the single drive source, the respective cylinders and the like of the printing press are driven through a gear mechanism, and a die and the like of the puncher are driven through a gear mechanism.
Incidentally, in the processing apparatus described above, since large power is required for a punching process by the puncher, load variations at the time of the punching are large, and the load variations are transmitted to other portions of the machine through the gears. There is a possibility that phase deviations can occur on printing products in the puncher and a printing unit owing to the transmission of the load variations. Moreover, a phenomenon that the gears rotate reversely (or stop) occurs owing to the load variations, and when the phenomenon reaches the printing unit, a state where the cylinders do not move occurs for a moment during the printing. Thus, a stripe (a shock streak) is formed in the printing portion, causing a printing failure.
It is an object of the present invention, in the printing press including the printing unit and the machining unit in series, to eliminate a phase change between the printing unit and the machining unit, and to eliminate the printing failure.